Technologies for Secure I/O with Accelerator Devices

ABSTRACT

Technologies for secure I/O data transfer with an accelerator device include a computing device having a processor and an accelerator. The processor establishes a trusted execution environment. The trusted execution environment may generate an authentication tag based on a memory-mapped I/O transaction, write the authentication tag to a register of the accelerator, and dispatch the transaction to the accelerator. The accelerator performs a cryptographic operation associated with the transaction, generates an authentication tag based on the transaction, and compares the generated authentication tag to the authentication tag received from the trusted execution environment. The accelerator device may initialize an authentication tag in response to a command from the trusted execution environment, transfer data between host memory and accelerator memory, perform a cryptographic operation in response to transferring the data, and update the authentication tag in response to transferrin the data. Other embodiments are described and claimed.

CLAIM TO PRIORITY

This Application is a continuation of and claims the benefit of andpriority to U.S. application Ser. No. 16/232,146, entitled TECHNOLOGIESFOR SECURE I/O WITH ACCELERATOR DEVICES, by Reshma Lal, et al., filedDec. 26, 2019, now allowed, which claims the benefit of and priority toU.S. Provisional Patent Application No. 62/687,403, filed Jun. 20, 2018,the entire contents of which are incorporated herein by reference.

BACKGROUND

Current processors may provide support for a trusted executionenvironment such as a secure enclave. Secure enclaves include segmentsof memory (including code and/or data) protected by the processor fromunauthorized access including unauthorized reads and writes. Inparticular, certain processors may include Intel® Software GuardExtensions (SGX) to provide secure enclave support. In particular, SGXprovides confidentiality, integrity, and replay-protection to the secureenclave data while the data is resident in the platform memory and thusprovides protection against both software and hardware attacks. Theon-chip boundary forms a natural security boundary, where data and codemay be stored in plaintext and assumed to be secure. Intel® SGX does notprotect I/O data that moves across the on-chip boundary.

Modern computing devices may include general-purpose processor cores aswell as a variety of hardware accelerators for offloadingcompute-intensive workloads or performing specialized tasks. Hardwareaccelerators may include, for example, one or more field-programmablegate arrays (FPGAs), which may include programmable digital logicresources that may be configured by the end user or system integrator.Hardware accelerators may also include one or more application-specificintegrated circuits (ASICs). Hardware accelerators may be embodied asI/O devices that communicate with the processor core over an I/Ointerconnect.

BRIEF DESCRIPTION OF THE DRAWINGS

The concepts described herein are illustrated by way of example and notby way of limitation in the accompanying figures. For simplicity andclarity of illustration, elements illustrated in the figures are notnecessarily drawn to scale. Where considered appropriate, referencelabels have been repeated among the figures to indicate corresponding oranalogous elements.

FIG. 1 is a simplified block diagram of at least one embodiment of acomputing device for secure I/O with an accelerator device;

FIG. 2 is a simplified block diagram of at least one embodiment of anaccelerator device of the computing device of FIG. 1;

FIG. 3 is a simplified block diagram of at least one embodiment of anenvironment of the computing device of FIGS. 1-2;

FIG. 4 is a simplified flow diagram of at least one embodiment of amethod for secure memory-mapped I/O writes that may be executed by acomputing device of FIGS. 1-3;

FIG. 5 is a simplified flow diagram of at least one embodiment of amethod for secure memory-mapped I/O writes that may be executed by anaccelerator device of FIGS. 1-3;

FIG. 6 is a simplified flow diagram of at least one embodiment of amethod for secure memory-mapped I/O reads that may be executed by acomputing device of FIGS. 1-3;

FIG. 7 is a simplified flow diagram of at least one embodiment of amethod for secure memory-mapped I/O reads that may be executed by theaccelerator device of FIGS. 1-3;

FIG. 8 is a simplified flow diagram of at least one embodiment of amethod for secure direct memory access transactions that may be executedby the computing device of FIGS. 1-3; and

FIG. 9 is a simplified flow diagram of at least one embodiment of amethod for secure direct memory access transactions that may be executedby the accelerator device of FIGS. 1-3.

DETAILED DESCRIPTION OF THE DRAWINGS

While the concepts of the present disclosure are susceptible to variousmodifications and alternative forms, specific embodiments thereof havebeen shown by way of example in the drawings and will be describedherein in detail. It should be understood, however, that there is nointent to limit the concepts of the present disclosure to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives consistent with the presentdisclosure and the appended claims.

References in the specification to “one embodiment,” “an embodiment,”“an illustrative embodiment,” etc., indicate that the embodimentdescribed may include a particular feature, structure, orcharacteristic, but every embodiment may or may not necessarily includethat particular feature, structure, or characteristic. Moreover, suchphrases are not necessarily referring to the same embodiment. Further,when a particular feature, structure, or characteristic is described inconnection with an embodiment, it is submitted that it is within theknowledge of one skilled in the art to effect such feature, structure,or characteristic in connection with other embodiments whether or notexplicitly described. Additionally, it should be appreciated that itemsincluded in a list in the form of “at least one A, B, and C” can mean(A); (B); (C); (A and B); (A and C); (B and C); or (A, B, and C).Similarly, items listed in the form of “at least one of A, B, or C” canmean (A); (B); (C); (A and B); (A and C); (B and C); or (A, B, and C).

The disclosed embodiments may be implemented, in some cases, inhardware, firmware, software, or any combination thereof. The disclosedembodiments may also be implemented as instructions carried by or storedon a transitory or non-transitory machine-readable (e.g.,computer-readable) storage medium, which may be read and executed by oneor more processors. A machine-readable storage medium may be embodied asany storage device, mechanism, or other physical structure for storingor transmitting information in a form readable by a machine (e.g., avolatile or non-volatile memory, a media disc, or other media device).

In the drawings, some structural or method features may be shown inspecific arrangements and/or orderings. However, it should beappreciated that such specific arrangements and/or orderings may not berequired. Rather, in some embodiments, such features may be arranged ina different manner and/or order than shown in the illustrative figures.Additionally, the inclusion of a structural or method feature in aparticular figure is not meant to imply that such feature is required inall embodiments and, in some embodiments, may not be included or may becombined with other features.

Referring now to FIG. 1, a computing device 100 for secure I/O with anaccelerator device includes a processor 120 and an accelerator device136, such as a field-programmable gate array (FPGA). In use, asdescribed further below, a trusted execution environment (TEE)established by the processor 120 securely communicates data with theaccelerator 136. Data may be transferred using memory-mapped I/O (MMIO)transactions or direct memory access (DMA) transactions. For example,the TEE may perform an MMIO write transaction that includes encrypteddata, and the accelerator 136 decrypts the data and performs the write.As another example, the TEE may perform an MMIO read requesttransaction, and the accelerator 136 may read the requested data,encrypt the data, and perform an MMIO read response transaction thatincludes the encrypted data. As yet another example, the TEE mayconfigure the accelerator 136 to perform a DMA operation, and theaccelerator 136 performs a memory transfer, performs a cryptographicoperation (i.e., encryption or decryption), and forwards the result. Asdescribed further below, the TEE and the accelerator 136 generateauthentication tags (ATs) for the transferred data and may use those ATsto validate the transactions. The computing device 100 may thus keepuntrusted software of the computing device 100, such as the operatingsystem or virtual machine monitor, outside of the trusted code base(TCB) of the TEE and the accelerator 136. Thus, the computing device 100may secure data exchanged or otherwise processed by a TEE and anaccelerator 136 from an owner of the computing device 100 (e.g., a cloudservice provider) or other tenants of the computing device 100.Accordingly, the computing device 100 may improve security andperformance for multi-tenant environments by allowing secure use ofaccelerator devices.

The computing device 100 may be embodied as any type of device capableof performing the functions described herein. For example, the computingdevice 100 may be embodied as, without limitation, a computer, a laptopcomputer, a tablet computer, a notebook computer, a mobile computingdevice, a smartphone, a wearable computing device, a multiprocessorsystem, a server, a workstation, and/or a consumer electronic device. Asshown in FIG. 1, the illustrative computing device 100 includes aprocessor 120, an I/O subsystem 124, a memory 130, and a data storagedevice 132. Additionally, in some embodiments, one or more of theillustrative components may be incorporated in, or otherwise form aportion of, another component. For example, the memory 130, or portionsthereof, may be incorporated in the processor 120 in some embodiments.

The processor 120 may be embodied as any type of processor capable ofperforming the functions described herein. For example, the processor120 may be embodied as a single or multi-core processor(s), digitalsignal processor, microcontroller, or other processor orprocessing/controlling circuit. As shown, the processor 120illustratively includes secure enclave support 122, which allows theprocessor 120 to establish a trusted execution environment known as asecure enclave, in which executing code may be measured, verified,and/or otherwise determined to be authentic. Additionally, code and dataincluded in the secure enclave may be encrypted or otherwise protectedfrom being accessed by code executing outside of the secure enclave. Forexample, code and data included in the secure enclave may be protectedby hardware protection mechanisms of the processor 120 while beingexecuted or while being stored in certain protected cache memory of theprocessor 120. The code and data included in the secure enclave may beencrypted when stored in a shared cache or the main memory 130. Thesecure enclave support 122 may be embodied as a set of processorinstruction extensions that allows the processor 120 to establish one ormore secure enclaves in the memory 130. For example, the secure enclavesupport 122 may be embodied as Intel® Software Guard Extensions (SGX)technology.

The memory 130 may be embodied as any type of volatile or non-volatilememory or data storage capable of performing the functions describedherein. In operation, the memory 130 may store various data and softwareused during operation of the computing device 100 such as operatingsystems, applications, programs, libraries, and drivers. As shown, thememory 130 may be communicatively coupled to the processor 120 via theI/O subsystem 124, which may be embodied as circuitry and/or componentsto facilitate input/output operations with the processor 120, the memory130, and other components of the computing device 100. For example, theI/O subsystem 124 may be embodied as, or otherwise include, memorycontroller hubs, input/output control hubs, sensor hubs, hostcontrollers, firmware devices, communication links (i.e., point-to-pointlinks, bus links, wires, cables, light guides, printed circuit boardtraces, etc.) and/or other components and subsystems to facilitate theinput/output operations. In some embodiments, the memory 130 may bedirectly coupled to the processor 120, for example via an integratedmemory controller hub. Additionally, in some embodiments, the I/Osubsystem 124 may form a portion of a system-on-a-chip (SoC) and beincorporated, along with the processor 120, the memory 130, theaccelerator device 136, and/or other components of the computing device100, on a single integrated circuit chip. Additionally or alternatively,in some embodiments the processor 120 may include an integrated memorycontroller and a system agent, which may be embodied as a logic block inwhich data traffic from processor cores and I/O devices converges beforebeing sent to the memory 130.

As shown, the I/O subsystem 124 includes a direct memory access (DMA)engine 126 and a memory-mapped I/O (MMIO) engine 128. The processor 120,including secure enclaves established with the secure enclave support122, may communicate with the accelerator device 136 with one or moreDMA transactions using the DMA engine 126 and/or with one or more MMIOtransactions using the MMIO engine 128. The computing device 100 mayinclude multiple DMA engines 126 and/or MMIO engines 128 for handlingDMA and MMIO read/write transactions based on bandwidth between theprocessor 120 and the accelerator 136. Although illustrated as beingincluded in the I/O subsystem 124, it should be understood that in someembodiments the DMA engine 126 and/or the MMIO engine 128 may beincluded in other components of the computing device 100 (e.g., theprocessor 120, memory controller, or system agent), or in someembodiments may be embodied as separate components.

The data storage device 132 may be embodied as any type of device ordevices configured for short-term or long-term storage of data such as,for example, memory devices and circuits, memory cards, hard diskdrives, solid-state drives, non-volatile flash memory, or other datastorage devices. The computing device 100 may also include acommunications subsystem 134, which may be embodied as any communicationcircuit, device, or collection thereof, capable of enablingcommunications between the computing device 100 and other remote devicesover a computer network (not shown). The communications subsystem 134may be configured to use any one or more communication technology (e.g.,wired or wireless communications) and associated protocols (e.g.,Ethernet, Bluetooth®, Wi-Fi®, WiMAX, 3G, 4G LTE, etc.) to effect suchcommunication.

The accelerator device 136 may be embodied as a field-programmable gatearray (FPGA), an application-specific integrated circuit (ASIC), acoprocessor, or other digital logic device capable of performingaccelerated functions (e.g., accelerated application functions,accelerated network functions, or other accelerated functions).Illustratively, the accelerator device 136 is an FPGA, which may beembodied as an integrated circuit including programmable digital logicresources that may be configured after manufacture. The FPGA mayinclude, for example, a configurable array of logic blocks incommunication over a configurable data interchange. The acceleratordevice 136 may be coupled to the processor 120 via a high-speedconnection interface such as a peripheral bus (e.g., a PCI Express bus)or an inter-processor interconnect (e.g., an in-die interconnect (IDI)or QuickPath Interconect (QPI)), or via any other appropriateinterconnect. The accelerator device 136 may receive data and/orcommands for processing from the processor 120 and return results datato the processor 120 via DMA, MMIO, or other data transfer transactions.

As shown, the computing device 100 may further include one or moreperipheral devices 138. The peripheral devices 138 may include anynumber of additional input/output devices, interface devices, hardwareaccelerators, and/or other peripheral devices. For example, in someembodiments, the peripheral devices 138 may include a touch screen,graphics circuitry, a graphical processing unit (GPU) and/or processorgraphics, an audio device, a microphone, a camera, a keyboard, a mouse,a network interface, and/or other input/output devices, interfacedevices, and/or peripheral devices.

Referring now to FIG. 2, an illustrative embodiment of afield-programmable gate array (FPGA) 200 is shown. As shown, the FPGA200 is one potential embodiment of an accelerator device 136. Theillustratively FPGA 200 includes a secure MMIO engine 202, a secure DMAengine 204, one or more accelerator functional units (AFUs) 206, andmemory/registers 208. As described further below, the secure MMIO engine202 and the secure DMA engine 204 perform in-line authenticatedcryptographic operations on data transferred between the processor 120(e.g., a secure enclave established by the processor) and the FPGA 200(e.g., one or more AFUs 206). In some embodiments, the secure MMIOengine 202 and/or the secure DMA engine 204 may intercept, filter, orotherwise process data traffic on one or more cache-coherentinterconnects, internal buses, or other interconnects of the FPGA 200.

Each AFU 206 may be embodied as logic resources of the FPGA 200 that areconfigured to perform an acceleration task. Each AFU 206 may beassociated with an application executed by the computing device 100 in asecure enclave or other trusted execution environment. Each AFU 206 maybe configured or otherwise supplied by a tenant or other user of thecomputing device 100. For example, each AFU 206 may correspond to abitstream image programmed to the FPGA 200. As described further below,data processed by each AFU 206, including data exchanged with thetrusted execution environment, may be cryptographically protected fromuntrusted components of the computing device 100 (e.g., protected fromsoftware outside of the trusted code base of the tenant enclave). EachAFU 206 may access or otherwise process stored in the memory/registers208, which may be embodied as internal registers, cache, SRAM, storage,or other memory of the FPGA 200. In some embodiments, the memory 208 mayalso include external DRAM or other dedicated memory coupled to the FPGA200.

Referring now to FIG. 3, in an illustrative embodiment, the computingdevice 100 establishes an environment 300 during operation. Theillustrative environment 300 includes a trusted execution environment(TEE) 302 and the accelerator 136. The TEE 302 further includes a hostcryptographic engine 304, a transaction dispatcher 306, a host validator308, and a direct memory access (DMA) manager 310. The accelerator 136includes an accelerator cryptographic engine 312, an acceleratorvalidator 314, a memory mapper 316, an authentication tag (AT)controller 318, and a DMA engine 320. The various components of theenvironment 300 may be embodied as hardware, firmware, software, or acombination thereof. As such, in some embodiments, one or more of thecomponents of the environment 300 may be embodied as circuitry orcollection of electrical devices (e.g., host cryptographic enginecircuitry 304, transaction dispatcher circuitry 306, host validatorcircuitry 308, DMA manager circuitry 310, accelerator cryptographicengine circuitry 312, accelerator validator circuitry 314, memory mappercircuitry 316, AT controller circuitry 318, and/or DMA engine circuitry320). It should be appreciated that, in such embodiments, one or more ofthe host cryptographic engine circuitry 304, the transaction dispatchercircuitry 306, the host validator circuitry 308, the DMA managercircuitry 310, the accelerator cryptographic engine circuitry 312, theaccelerator validator circuitry 314, the memory mapper circuitry 316,the AT controller circuitry 318, and/or the DMA engine circuitry 320 mayform a portion of the processor 120, the I/O subsystem 124, theaccelerator 136, and/or other components of the computing device 100.Additionally, in some embodiments, one or more of the illustrativecomponents may form a portion of another component and/or one or more ofthe illustrative components may be independent of one another.

The TEE 302 may be embodied as a trusted execution environment of thecomputing device 100 that is authenticated and protected fromunauthorized access using hardware support of the computing device 100,such as the secure enclave support 122 of the processor 120.Illustratively, the TEE 302 may be embodied as one or more secureenclaves established using Intel SGX technology. The TEE 302 may alsoinclude or otherwise interface with one or more drivers, libraries, orother components of the computing device 100 to interface with theaccelerator 136.

The host cryptographic engine 304 is configured to generate anauthentication tag (AT) based on a memory-mapped I/O (MMIO) transactionand to write that AT to an AT register of the accelerator 136. For anMMIO write request, the host cryptographic engine 304 is furtherconfigured to encrypt a data item to generate an encrypted data item,and the AT is generated in response to encrypting the data item. For anMMIO read request, the AT is generated based on an address associatedwith MMIO read request.

The transaction dispatcher 306 is configured to dispatch thememory-mapped I/O transaction (e.g., an MMIO write request or an MMIOread request) to the accelerator 136 after writing the calculated AT tothe AT register. An MMIO write request may be dispatched with theencrypted data item.

The host validator 308 may be configured to verify that an MMIO writerequest succeeded in response dispatching the MMIO write request.Verifying that the MMIO write request succeeded may include securelyreading a status register of the accelerator 136, securely reading avalue at the address of the MMIO write from the accelerator 136, orreading an AT register of the accelerator 136 that returns an AT valuecalculated by the accelerator 136, as described below. For MMIO readrequests, the host validator 308 may be further configured to generatean AT based on an encrypted data item included in a MMIO read responsedispatched from the accelerator 136; read a reported AT from a registerof the accelerator 136; and determine whether the AT generated by theTEE 302 matches the AT reported by the accelerator 136. The hostvalidator 308 may be further configured to indicate an error if thoseATs do not match, which provides assurance that data was not modified onthe way from the TEE 302 to the accelerator 136.

The accelerator cryptographic engine 312 is configured to perform acryptographic operation associated with the MMIO transaction and togenerate an AT based on the MMIO transaction in response to the MMIOtransaction being dispatched. For an MMIO write request, thecryptographic operation includes decrypting an encrypted data itemreceived from the TEE 302 to generate a data item, and the AT isgenerated based on the encrypted data item. For an MMIO read request,the cryptographic operation includes encrypting a data item from amemory of the accelerator 136 to generate an encrypted data item, andthe AT is generated based on that encrypted data item.

The accelerator validator 314 is configured to determine whether the ATwritten by the TEE 302 matches the AT determined by the accelerator 136.The accelerator validator 314 is further configured to drop the MMIOtransaction if those ATs do not match. For MMIO read requests, theaccelerator validator 314 may be configured to generate a poisoned AT inresponse to dropping the MMIO read request, and may be furtherconfigured to dispatch a MMIO read response with a poisoned data item tothe TEE 302 in response to dropping the MMIO read request.

The memory mapper 316 is configured to commit the MMIO transaction inresponse to determining that the AT written by the TEE 302 matches theAT generated by the accelerator 136. For an MMIO write request,committing the transaction may include storing the data item in a memoryof the accelerator 136. The memory mapper 316 may be further configuredto set a status register to indicate success in response to storing thedata item. For an MMIO read request, committing the transaction mayinclude reading the data item at the address in the memory of theaccelerator 136 and dispatching an MMIO read response with the encrypteddata item to the TEE 302.

The DMA manager 310 is configured to securely write an initializationcommand to the accelerator 136 to initialize a secure DMA transfer. TheDMA manager 310 is further configured to securely configure a descriptorindicative of a host memory buffer, an accelerator 136 buffer, and atransfer direction. The transfer direction may be host to accelerator136 or accelerator 136 to host. The DMA manager 310 is furtherconfigured to securely write a finalization command to the accelerator136 to finalize an authentication tag (AT) for the secure DMA transfer.The initialization command, the descriptor, and the finalization commandmay each be securely written and/or configured with an MMIO writerequest. The DMA manager 310 may be further configured to determinewhether to transfer additional data in response to securely configuringthe descriptor, the finalization command may be securely written inresponse to determining that no additional data remains for transfer.

The AT controller 318 is configured to initialize an AT in response tothe initialization command from the TEE 302. The AT controller 318 isfurther configured to finalize the AT in response to the finalizationcommand from the TEE 302.

The DMA engine 320 is configured to transfer data between the hostmemory buffer and the accelerator 136 buffer in response to thedescriptor from the TEE 302. For a transfer from host to accelerator136, transferring the data includes copying encrypted data from the hostmemory buffer and forwarding the plaintext data to the accelerator 136buffer in response to decrypting the encrypted data. For a transfer fromaccelerator 136 to host, transferring the data includes copyingplaintext data from the accelerator 136 buffer and forwarding encrypteddata to the host memory buffer in response encrypting the plaintextdata.

The accelerator cryptographic engine 312 is configured to perform acryptographic operation with the data in response to transferring thedata and to update the AT in response to transferring the data. For atransfer from host to accelerator 136, performing the cryptographicoperation includes decrypting encrypted data to generate plaintext data.For a transfer from accelerator 136 to host, performing thecryptographic operation includes encrypting plaintext data to generateencrypted data.

The host validator 308 is configured to determine an expected AT basedon the secure DMA transfer, to read the AT from the accelerator 136 inresponse to securely writing the finalization command, and to determinewhether the AT from the accelerator 136 matches the expected AT. Thehost validator 308 may be further configured to indicate success if theATs match and to indicate failure if the ATs do not match.

Referring now to FIG. 4, in use, the computing device 100 may execute amethod 400 for secure memory-mapped I/O (MMIO) write requests. It shouldbe appreciated that, in some embodiments, the operations of the method400 may be performed by one or more components of the environment 300 ofthe computing device 100 as shown in FIG. 3, such as the trustedexecution environment 302. The method 400 begins in block 402, in whichthe TEE 302 encrypts data with a data key. The data may be embodied as a32-bit value, a 64-bit value, or other relatively small data item. Forexample, the data may be a value or values that are to be written to aregister or other memory location of the accelerator 136 (e.g., aregister 208 associated with an AFU 206). The data key may be securelyprovisioned to both the TEE 302 and the accelerator 136 ahead of timeusing any appropriate technique. The data is illustratively encryptedwith the AES Galois/counter mode (AES-GCM) authenticated encryptionalgorithm. In other embodiments, the data may be encrypted with anyother appropriate cryptographic algorithm.

In block 404, the TEE 302 generates an authentication tag (AT) for theMMIO write request with the encrypted data. As described above, the ATmay be generated with the encrypted data using an authenticatedencryption algorithm such as AES-GCM. The AT may be embodied as anyhash, message authentication code, or other value that may be used toauthenticated the encrypted data and additional authenticated data. Theadditional authenticated data may include, for example, an addressassociated with the MMIO write request, such as a memory address,register offset, or other addressing information.

In block 406, the TEE 302 writes the AT to an AT register of theaccelerator 136. The AT may be written with an unsecure MMIO or otheroperation. For example, the AT may be embodied as a 128-bit value andmay be written to the accelerator 136 with two 64-bit unsecure writeoperations. Note that if the AT is intercepted or otherwise modified bya malicious actor, then as described further below, the accelerator 136will determine that the MMIO write is invalid and will drop the MMIOwrite.

In block 408, the TEE 302 dispatches the MMIO write request to transferthe encrypted data from the host (i.e., the TEE 302, an associateddriver, or other software executed by the processor 120) to theaccelerator 136. The MMIO write request may be dispatched using anunsecure MMIO engine 128 or other MMIO component of the computing device100. As described below in connection with FIG. 5, a secure MMIOcomponent of the accelerator 136 (e.g., the secure MMIO 202 of an FPGA200) decrypts and verifies the MMIO write request transaction.

In block 410, the TEE 302 may verify that the MMIO write requestsucceeded. Additionally or alternatively, in certain situations theremay be no need to verify that the MMIO write request succeeded, in whichcase the TEE 302 may omit verifying that the MMIO write requestsucceeded. For example, the TEE 302 may only verify MMIO write requeststo registers of the accelerator 136 that could affect the reliability ofresults. As another example, if failure to successfully perform the MMIOwrite request can be detected later in a different operation,verification of the MMIO write request may be omitted.

The TEE 302 may use any appropriate technique to verify that the MMIOwrite request was successfully performed by the accelerator 136. In someembodiments, in block 412, the TEE 302 may securely read a statusregister of the accelerator 136. The status register may be set by theaccelerator 136 if the MMIO write was performed successfully. To performthe secure read, the TEE 302 may execute a secure MMIO read request asdescribed below in connection with FIGS. 6-7. In some embodiments, inblock 414, the TEE 302 may securely read a value back from theaccelerator 136 at the address of the MMIO write (e.g., read back thesame register). The TEE 302 may compare the value read from theaccelerator 136 with the original data item and determine whether thosevalues match. The value may be read with a secure MMIO read request asdescribed below in connection with FIGS. 6-7. Reading back the value maynot be possible for registers or memory locations with side effects orfor write-only registers or memory locations. In some embodiments, inblock 416, the TEE 302 may read an AT from the accelerator 136 that isgenerated by the accelerator 136. The TEE 302 may compare the AT readfrom the accelerator 136 with the AT generated by the TEE 302 anddetermine whether those ATs match. The AT may be read with one or moreunsecure MMIO read requests or other transfers. In some embodiments,each AT may be a 128-bit value, and thus reading the AT may require two64-bit MMIO read operations. The AT does not need to be read securely,because by modifying an AT, an attacker could only create a denial ofservice attack, as verification will fail and the TEE 302 will considerthe transfer to have failed.

In block 418, the TEE 302 checks whether the MMIO write request wascompleted successfully. If not, the method 400 braches to block 420, inwhich the TEE 302 may indicate an error or otherwise indicate that theMMIO write request was not successful. In response, the TEE 302 mayhalt, retry the MMIO write, or perform another operation. Referring backto block 418, if the MMIO write request was completed successfully, themethod 400 loops back to block 402 to perform additional MMIO writerequests.

Referring now to FIG. 5, in use, the computing device 100 may execute amethod 500 for secure MMIO write requests. It should be appreciatedthat, in some embodiments, the operations of the method 500 may beperformed by one or more components of the environment 300 of thecomputing device 100 as shown in FIG. 3, such as the accelerator 136.The method 500 begins in block 502, in which the accelerator 136 storesan authentication tag (AT) value received from the TEE 302. As describedabove, the AT is generated by the TEE 302 based on the encrypted dataitem that is to be written to the accelerator 136. The AT may be writtenwith an unsecure MMIO write or other operation. For example, the AT maybe embodied as a 128-bit value and may be written to the accelerator 136with two 64-bit unsecure write operations.

In block 504, the accelerator 136 receives an MMIO write requesttransaction to transfer encrypted data from the host (i.e., the TEE 302,an associated driver, or other software executed by the processor 120)to the accelerator 136. As described above, the MMIO write request maybe received from an unsecure MMIO engine 128 or other MMIO component ofthe computing device 100. The encrypted data may be embodied as a 32-bitvalue, a 64-bit value, or other relatively small data item. The MMIOwrite request may include the encrypted data as well as an associatedaddress such as a memory address, register offset, or other addressinginformation.

In block 506, the accelerator 136 decrypts the encrypted data using adata key. As described above, the data key may be securely provisionedto both the TEE 302 and the accelerator device 136 ahead of time usingany appropriate technique. The data is illustratively decrypted with theAES Galois/counter mode (AES-GCM) authenticated decryption algorithm. Inother embodiments, the data may be decrypted with any other appropriatecryptographic algorithm. The plaintext data generated from decryptionmay be a value or values that are to be written to a register or othermemory location of the accelerator 136 (e.g., a register 208 associatedwith an AFU 206).

In block 508, the accelerator 136 generates an AT for the MMIO writerequest using the encrypted data received from the TEE 302. As describedabove, the AT may be generated based on the encrypted data using anauthenticated encryption algorithm such as AES-GCM. The AT may beembodied as any hash, message authentication code, or other value thatmay be used to authenticated the encrypted data and additionalauthenticated data. The additional authenticated data may include, forexample, the address associated with the MMIO write.

In block 510, the accelerator 136 determines whether the AT generated bythe accelerator 136 matches the AT written by the TEE 302. If not, themethod 500 branches to block 516, described below. If the AT valuesmatch, the method 500 advances to block 512.

In block 512, the accelerator 136 stores the decrypted, plaintext datain an accelerator 136 memory, register, or other storage location. Forexample, the plaintext data may be stored in a register 208 of an FPGA200, in another memory 208 included in the FPGA 200, or in an externalmemory device coupled to the FPGA 200. The register or storage locationmay be identified with the address of the MMIO write transaction. Afterbeing stored, the plaintext data may be processed or otherwise accessedby the accelerator 136, for example by an AFU 206 of the FPGA 200. Insome embodiments, in block 514 the accelerator 136 may set a statusregister to indicate the MMIO write request was performed successfully.As described above, the TEE 302 may securely read the status register toverify the MMIO write request. After committing the MMIO write requestand in some embodiments setting the status register, the method 500loops back to block 502 to perform additional MMIO write requests.

Referring back to block 510, if the AT generated by the accelerator 136and the AT written by the TEE 302 do not match, then the method 500branches to block 516, in which the accelerator 136 drops the MMIO writetransaction. The accelerator 136 may also set a status register toindicate that the MMIO write request was not performed successfully. Theplaintext value is not written to the memory of the accelerator 136.Thus, the accelerator 136 may be protected from certain maliciousattacks. For example, a malicious actor may submit a false MMIO writetransaction to the accelerator 136. In that circumstance, an AT valuewritten by the TEE 302 would not match the AT value calculated for thefalse MMIO transaction, and the malicious actor would not be able tocalculate a correct AT value because the data key is secret. As anotherexample, a malicious actor may write a false AT value to the accelerator136. In that circumstance, the AT value calculated by the accelerator136 based on the MMIO write request (e.g., the MMIO write requestdispatched by the TEE 302) would not match the false AT value, and theMMIO write request would be dropped. After dropping the MMIO writetransaction, the method 500 loops back to block 502 to performadditional MMIO write requests.

Referring now to FIG. 6, in use, the computing device 100 may execute amethod 600 for secure memory-mapped I/O read operations. As describedfurther below, an MMIO read operation includes two MMIO transactions, anMMIO read request and an MMIO read response. It should be appreciatedthat, in some embodiments, the operations of the method 600 may beperformed by one or more components of the environment 300 of thecomputing device 100 as shown in FIG. 3, such as the trusted executionenvironment 302. The method 600 begins in block 602, in which the TEE302 generates an authentication tag (AT) for an MMIO read request. TheAT may be generated using an authenticated encryption algorithm such asAES-GCM. Instead of generating the AT based on encrypted data, the ATmay be based on a known value, such as a block of 128 “zero” bits orother predetermined constant. The AT may be embodied as any hash,message authentication code, or other value that may be used toauthenticated the supplied value and additional authenticated data. Theadditional authenticated data may include, for example, an addressassociated with the MMIO read request, such as a memory address,register offset, or other addressing information.

In block 604, the TEE 302 writes the AT to an AT register of theaccelerator 136. The AT may be written with an unsecure MMIO write orother operation. For example, the AT may be embodied as a 128-bit valueand may be written to the accelerator 136 with two 64-bit unsecure writeoperations. Note that if the AT is intercepted or otherwise modified bya malicious actor, then as described further below, the accelerator 136will determine that the MMIO read request is invalid and will drop theMMIO read request.

In block 606, the TEE 302 dispatches the MMIO read request to theaccelerator 136. The MMIO read request may be dispatched using anunsecure MMIO engine 128 or other MMIO component of the computing device100. As described below in connection with FIG. 5, a secure MMIOcomponent of the accelerator 136 (e.g., the secure MMIO 202 of an FPGA200) decrypts and verifies the MMIO read request transaction. If theMMIO read request is successfully verified, the accelerator 136dispatches an MMIO read response.

In block 608, the TEE 302 receives an MMIO read response from theaccelerator 136. As described further below, the MMIO read response mayinclude encrypted data that was originally read by the accelerator 136from a memory, register, or other storage of the accelerator 136 andthen encrypted by the accelerator 136. The MMIO read response may bereceived using the unsecure MMIO engine 128 or other MMIO component ofthe computing device 100.

In block 610, the TEE 302 calculates an AT for the encrypted datareceived from the accelerator 136 with the MMIO read response. Asdescribed above, the AT may be generated with the encrypted data usingan authenticated encryption algorithm such as AES-GCM. The AT may beembodied as any hash, message authentication code, or other value thatmay be used to authenticated the encrypted data and additionalauthenticated data. The additional authenticated data may include, forexample, an address associated with the MMIO read response, such as amemory address, register offset, or other addressing information.

In block 612, the TEE 302 reads an AT register from the accelerator 136.The AT register includes an AT that was generated by the accelerator 136based on the MMIO read response. The AT may be read with one or moreunsecure MMIO reads. For example, the AT may be a 128-bit value, readingthe AT may require two 64-bit MMIO unsecure read operations. In block614, the TEE 302 compares the AT read from the accelerator 136 with theAT generated by the TEE 302 and determines whether those ATs match. Ifthe ATs do not match, then the method 600 branches to block 616, inwhich the TEE 302 may indicate an error or otherwise indicate that theMMIO read request was not successful. In response, the TEE 302 may halt,retry the MMIO read request, or perform another operation. Referringback to block 614, if the ATs match, the method 600 loops back to block602 to perform additional MMIO read requests. The TEE 302, anapplication, or other component of the computing device 100 may decryptthe encrypted data included with the MMIO read response and otherwiseprocess the received data.

Referring now to FIG. 7, in use, the computing device 100 may execute amethod 700 for secure memory-mapped I/O read operations. It should beappreciated that, in some embodiments, the operations of the method 700may be performed by one or more components of the environment 300 of thecomputing device 100 as shown in FIG. 3, such as the accelerator 136.The method 700 begins in block 702, in which the accelerator 136 storesan authentication tag (AT) value received from the TEE 302. As describedabove, the AT is generated by the TEE 302 based on an MMIO read request.The AT may be written with an unsecure MMIO or other operation. Forexample, the AT may be embodied as a 128-bit value and may be written tothe accelerator 136 with two 64-bit unsecure write operations.

In block 704, receives an MMIO read request that requests a transfer ofencrypted data from the accelerator 136 to the host (i.e., to the TEE302, an associated driver, or other software executed by the processor120). As described above, the MMIO read request may be received from anunsecure MMIO engine 128 or other MMIO component of the computing device100. The requested data may be embodied as a 32-bit value, a 64-bitvalue, or other relatively small data item. The MMIO read request mayspecify associated address such as a memory address, register offset, orother addressing information of the requested data.

In block 706, the accelerator 136 generates an AT for the MMIO readrequest based on the MMIO read request received from the TEE 302. Asdescribed above, the AT may be generated using an authenticatedencryption algorithm such as AES-GCM. Instead of generating the AT basedon encrypted data, the AT may be based on a known value, such as a blockof 128 “zero” bits or other predetermined constant. The AT may beembodied as any hash, message authentication code, or other value thatmay be used to authenticated the supplied value and additionalauthenticated data. The additional authenticated data may include, forexample, an address associated with the MMIO read request, such as amemory address, register offset, or other addressing information.

In block 708, the accelerator 136 determines whether the AT generated bythe accelerator 136 matches the AT written by the TEE 302. If not, themethod 700 branches to block 718, described below. If the AT valuesmatch, the method 700 advances to block 710.

In block 710, the accelerator 136 reads the requested plaintext datafrom a memory, register, or other storage location of the accelerator136. For example, the plaintext data may be read from a register 208 ofan FPGA 200, from another memory 208 included in the FPGA 200, or froman external memory device coupled to the FPGA 200. The register orstorage location may be identified with the address of the MMIO readrequest. The plaintext data may include acceleration results or otherdata generated by the accelerator 136, for example by an AFU 206 of theFPGA 200.

In block 712, the accelerator 136 encrypts the plaintext data using adata key. As described above, the data key may be securely provisionedto both the TEE 302 and the accelerator device 136 ahead of time usingany appropriate technique. The data is illustratively encrypted with theAES Galois/counter mode (AES-GCM) authenticated encryption algorithm. Inother embodiments, the data may be encrypted with any other appropriatecryptographic algorithm. The encrypted data generated from encryptionmay be a value or values that are to be returned to the TEE 302 as anMMIO read response.

In block 714, the accelerator 136 generates an AT for the MMIO readresponse using the encrypted data. As described above, the AT may begenerated with the encrypted data using an authenticated encryptionalgorithm such as AES-GCM. The AT may be embodied as any hash, messageauthentication code, or other value that may be used to authenticatedthe encrypted data and additional authenticated data. The additionalauthenticated data may include, for example, the address associated withthe MMIO read response.

In block 716, the accelerator 136 dispatches the MMIO read response tothe TEE 302. The MMIO read response includes the encrypted datagenerated by the accelerator 136. As described above, the MMIO readresponse may be received by the TEE 302 using the unsecure MMIO engine128 or other MMIO component of the computing device 100. Also asdescribed above, the TEE 302 may verify the MMIO read response byreading the AT calculated by the accelerator 136 from one or moreregisters of the accelerator 136. After dispatching the MMIO readresponse, the method 700 loops back to block 702 to perform additionalMMIO read operations.

Referring back to block 708, if the AT generated by the accelerator 136and the AT written by the TEE 302 do not match, then the method 500branches to block 718, in which the accelerator 136 drops the MMIO readrequest transaction. The accelerator 136 does not read the requestedvalue from the memory or other storage of the accelerator 136. In block720, in some embodiments, the accelerator 136 may store a poisoned ATvalue in an AT register. The poisoned AT value may be a predeterminedvalue, an AT generated based on a predetermined value, or anotherincorrect AT value. As described above, the TEE 302 reads the ATregister to verify the MMIO read response received from the accelerator136. The TEE 302 may determine that the MMIO read request was droppedbased on the poisoned AT value, for example, by determining that thepoisoned AT value does not match an AT value calculated over the MMIOread response. Similarly, in some embodiments, in block 722 theaccelerator 136 may dispatch an MMIO read response transaction withpoisoned data. The poisoned data may be embodied as, for example, apredetermined value or other constant that may be detected by the TEE302. As another example, the poisoned data may be an arbitrary valuethat, when verified by the TEE 302, does not match the poisoned ATvalue. After dropping the MMIO read request transaction, the method 700loops back to block 702 to continue processing MMIO read operations.

Referring now to FIG. 8, in use, the computing device 100 may execute amethod 800 for secure direct memory access (DMA) transfers. It should beappreciated that, in some embodiments, the operations of the method 800may be performed by one or more components of the environment 300 of thecomputing device 100 as shown in FIG. 3, such as the trusted executionenvironment 302. The method 800 begins in block 802, in which the TEE302 prepares one or more memory buffers for a DMA transfer. For example,the TEE 302 may allocate a circular buffer in the host memory 130. Asdescribed further below, the buffer may be divided into multiple blocksof data that may each be transferred in a single DMA transaction. Forexample, the buffer may include multiple 512-bit blocks. In someembodiments, the buffer may be aligned on a block boundary in the memory130 (e.g., 64-byte aligned). If the buffer is not aligned in memory,data located before the first block boundary and/or after the last blockboundary may be transferred using one or more secure MMIO operations, asdescribed above in connection with FIGS. 4-7. In some embodiments, inblock 804, the TEE 302 may encrypt data in the host buffer with a datakey for a host to accelerator 136 transfer. The data key may be securelyprovisioned to both the TEE 302 and the accelerator device 136 ahead oftime using any appropriate technique. The data is illustrativelyencrypted with the AES Galois/counter mode (AES-GCM) authenticatedencryption algorithm. In other embodiments, the data may be encryptedwith any other appropriate cryptographic algorithm.

In block 806, the TEE 302 securely commands the accelerator 136 toinitialize a secure DMA transfer. The TEE 302 may, for example, performa secure MMIO write to a register of the accelerator 136 to cause theaccelerator 136 to initialize the secure DMA transfer. As describedfurther below, the accelerator 136 may initialize an authentication tag(AT) and/or other state data in response to the command to initializethe secure DMA transfer.

In block 808, the TEE 302 securely configures a descriptor for the DMAtransfer. The TEE 302 may, for example, perform one or more secure MMIOwrites to a register, command buffer, or other address of theaccelerator 136 to provide the descriptor. The descriptor includes datadescribing the secure DMA transaction, including a source address, adestination address, a length, and a direction of transfer. Thedescriptor may also include additional data, such as a last flag thatinstructs the accelerator 136 to raise an interrupt or otherwise notifythe TEE 302 after performing the DMA transaction. In some embodiments,in block 810 the descriptor may indicate a host to accelerator 136transfer. In those embodiments the source address may identify a hostbuffer in the memory 130 that includes encrypted data, and thedestination address may identify an accelerator buffer in a memory ofthe accelerator 136. In some embodiments, in block 812 the descriptormay indicate an accelerator 136 to host transfer. In those embodimentsthe source address may identify an accelerator buffer in a memory of theaccelerator 136, and the destination address may identify a host bufferin the memory 130.

In some embodiments, the TEE 302 may program multiple descriptorssecurely and then instruct the accelerator 136 to start transferringdata. In those embodiments, the accelerator 136 will read the firstdescriptor and perform the transfer, and then read the second descriptorand perform the transfer, and so on, until the accelerator 136 hascompleted transfers for all programmed descriptors. The accelerator 136may then ask the TEE 302 if there are more transfers. The transfers willthus continue until the TEE 302 acting as master has completed alltransfers. At that point, the TEE 302 will issue a finalize command, asdescribed further below. After configuring the descriptor ordescriptors, the accelerator 136 performs the secure DMA transaction andupdates the corresponding AT as described further below in connectionwith FIG. 9.

In some embodiments, in block 814 the TEE 302 may wait for completion ofthe secure DMA transaction. For example, in some embodiments the TEE 302may wait for an interrupt raised by the accelerator 136 or the TEE 302may poll for a completion. In block 816, the TEE 302 determines whetheradditional DMA transactions remain to be executed. If additional DMAtransactions remain for transfer, the method 500 loops back to block 808to continue configuring descriptors for DMA transactions. For example,as described above, in some embodiments the source buffer may includemultiple 512-bit blocks that may each be transferred in a single DMAtransaction. The TEE 302 may continue to configure descriptors for eachblock until the entire buffer is transferred. Continuing that example,the TEE 302 may set the last flag for the last descriptor to betransferred and wait for an interrupt from the accelerator 136,indicating that all blocks have been transferred. As another example,the TEE 302 may divide the buffer into two sub-buffers, or ping-pongbuffers. The TEE 302 may configure descriptors for one of thesub-buffers and set the last flag for the last descriptor in thesub-buffer. On receiving the interrupt, the TEE 302 may similarlyconfigure the descriptors of the other sub-buffer. In that fashion, theTEE 302 may ensure that entries in a circular buffer are not overwrittenand that an interrupt will not be lost, because at most one of thedescriptors in flight has the last flag set. Referring back to block816, if no more DMA transactions remain to be executed, the method 800advances to block 818.

In block 818, the TEE 302 securely commands the accelerator 136 tofinalize the AT. As described above, the TEE 302 may, for example,perform a secure MMIO write to a register of the accelerator 136 tocause the accelerator 136 to finalize the AT. The accelerator 136 mayfinalize the AT as described below in connection with FIG. 9.

In block 820, the TEE 302 reads the AT from the accelerator 136. The TEE302 may read, for example, an AT register that includes an AT generatedby the accelerator 136 based on the DMA transactions performed by theaccelerator 136. The AT may be read with one or more unsecure MMIOreads. For example, the AT may be a 128-bit value, reading the AT mayrequire two 64-bit MMIO unsecure read operations.

In block 822, the TEE calculates an expected AT for encrypted dataassociated with the secure DMA transfer. As described above, the AT maybe generated with the encrypted data using an authenticated encryptionalgorithm such as AES-GCM. The AT may be embodied as any hash, messageauthentication code, or other value that may be used to authenticatedthe encrypted data and additional authenticated data. The encrypted dataused to generate the AT depends on the direction of transfer. In someembodiments, in block 824, the AT may be generated based on encryptedhost data in the host buffer for a host to accelerator 136 transfer. Theencrypted host data may be generated, for example, by the TEE 302, anapplication, or other entity of the computing device 100. In someembodiments, in block 826, the AT may be generated based on encrypteddata received from the accelerator 136 for an accelerator 136 to hosttransfer.

In block 828, the TEE 302 determines whether the AT read from theaccelerator 136 matches the expected AT. If so, the method 800 branchesto block 830, in which the TEE 302 may indicate that the secure DMAtransfer was completed successfully. The method 800 then loops back toblock 802 to perform additional secure DMA transfers. Referring back toblock 828, if the ATs do not match, then the method 800 branches toblock 832, in which the TEE 302 may indicate a failure or otherwiseindicate that the secure DMA transfer was not completed successfully.The TEE 302 may halt, retry the DMA transaction, or perform anotheroperation. The method 800 may then loop back to block 802 to performadditional secure DMA transfers.

Referring now to FIG. 9, in use, the computing device 100 may execute amethod 900 for secure direct memory access transfers. It should beappreciated that, in some embodiments, the operations of the method 900may be performed by one or more components of the environment 300 of thecomputing device 100 as shown in FIG. 3, such as the accelerator 136.The method 900 begins in block 902, in which the accelerator 136monitors for secure commands received from the host (e.g., from the TEE302). For example, the accelerator 136 may monitor for secure MMIO writerequests to one or more registers, descriptor queues, or other memorylocations of the accelerator device 136.

In block 904, the accelerator 136 determines whether a command toinitialize a secure DMA transfer has been received. If not, the method900 advances to block 908, described below. If a command to initializethe secure DMA transfer is received, the method 900 branches to block906, in which the accelerator 136 initializes an authentication tag(AT). The accelerator 136 may, for example, initialize one or moreregisters, start one or more encryption pipelines, pre-calculate masks,or otherwise prepare the accelerator 136 for calculating AT values.After initializing the AT, the method 900 loops back to block 902 tocontinue monitoring for commands.

In block 908, the accelerator 136 determines whether a descriptor hasbeen configured. If not, the method 900 advances to block 928, describedbelow. If a descriptor has been configured, the method 900 branches toblock 910, in which the accelerator 136 transfers data by executing aDMA transaction based on the descriptor. The accelerator 136 maytransfer the data, for example, using one or more DMA engines or othercomponents of the accelerator 136. The particular data transferreddepends on the direction of transfer, which is indicated by thedescriptor. The descriptor also provides a source address and adestination address for the transfer. In some embodiments, for host toaccelerator 136 transfers, in block 912 the accelerator 136 may copyencrypted data from the host memory 130 to the accelerator 136. In someembodiments, for accelerator 136 to host transfers, in block 914 theaccelerator 136 may copy plaintext data from a memory, register, orother storage of the accelerator 136.

In block 916, the accelerator 136 performs a cryptographic operation onthe transferred data using a data key. The accelerator 136 may, forexample, intercept the data transfer on a cache-coherent interconnect orother internal interconnect of the accelerator 136. As described above,the data key may be securely provisioned to both the TEE 302 and theaccelerator 136 ahead of time using any appropriate technique. Thecryptographic operation is illustratively an AES Galois/counter mode(AES-GCM) authenticated cryptographic algorithm. The accelerator 136also updates the AT based on encrypted data associated with the DMAtransfer. The particular cryptographic operation performed depends onthe direction of the transfer. In some embodiments, for host toaccelerator 136 transfers, in block 918 the accelerator 136 decryptsencrypted data received from the host to recover the plaintext data. Theaccelerator 136 updates the AT based on the encrypted data received fromthe host. In some embodiments, for accelerator 136 to host transfers, inblock 920 the accelerator 136 encrypts plaintext data from theaccelerator 136 memory and generates the encrypted data. The accelerator136 updates the AT based on the encrypted data generated by theaccelerator 136.

In block 922, the accelerator 136 forwards the results of thecryptographic operation to the appropriate destination. The accelerator136 may, for example, forward the results on the cache-coherentinterconnect or other internal interconnect of the accelerator 136. Boththe particular data forwarded and the destination depend on thedirection of the transfer. In some embodiments, for host to accelerator136 transfers, in block 924 the accelerator 136 forwards the decrypted,plaintext data to the memory of the accelerator 136. After the plaintextdata is stored in the accelerator 136 memory, the accelerator 136 mayprocess the data, for example with an AFU 206 of the FPGA 200. In someembodiments, for accelerator 136 to host transfers, in block 926 theaccelerator 136 forwards the encrypted data to the host memory 130. Theencrypted data may be stored in a host buffer in the memory 130. Aftertransfer, the encrypted data may be copied, decrypted, and/or otherwiseprocessed by the TEE 302, by an application, or by another component ofthe computing device 100. After forwarding the results of thecryptographic operation, the method 900 loops back to block 902 tocontinue monitoring for commands.

In block 928, the accelerator 136 determines whether a command tofinalize the AT has been received. If not, the method 900 loops back toblock 902 to continue monitoring for commands. If a command to finalizethe AT was received, the method 900 branches to block 930, in which theaccelerator 136 finalizes the AT and stores the final AT value in aregister. The accelerator 136 may perform any appropriate calculation tofinalize the AT. For example, the AT may be updated based on the finallength of all of the DMA transfers. As described above, the final ATvalue may be read by the TEE 302 to verify that the secure DMA transferwas performed successfully. After storing the AT value, the method 900loops back to block 902 to continue monitoring for commands.

It should be appreciated that, in some embodiments, the methods 400,500, 600, 700, 800, and/or 900 may be embodied as various instructionsstored on a computer-readable media, which may be executed by theprocessor 120, the I/O subsystem 124, the accelerator 136, and/or othercomponents of the computing device 100 to cause the computing device 100to perform the respective method 400, 500, 600, 700, 800, and/or 900.The computer-readable media may be embodied as any type of media capableof being read by the computing device 100 including, but not limited to,the memory 130, the data storage device 132, firmware devices, othermemory or data storage devices of the computing device 100, portablemedia readable by a peripheral device 138 of the computing device 100,and/or other media.

EXAMPLES

Illustrative examples of the technologies disclosed herein are providedbelow. An embodiment of the technologies may include any one or more,and any combination of, the examples described below.

Example 1 includes a computing device for secure data transfer, thecomputing device comprising a trusted execution environment and anaccelerator device; wherein: the trusted execution environmentcomprises: a host cryptographic engine to (i) generate a firstauthentication tag based on a memory-mapped I/O transaction and (ii)write the first authentication tag to an authentication tag register ofan accelerator device of the computing device; and a transactiondispatcher to dispatch the memory-mapped I/O transaction to theaccelerator device in response to writing of the first authenticationtag; and the accelerator device comprises: an accelerator cryptographicengine to (i) perform a cryptographic operation associated with thememory-mapped I/O transaction in response to dispatch of thememory-mapped I/O transaction and (ii) generate a second authenticationtag based on the memory-mapped I/O transaction in response to thedispatch of the memory-mapped I/O transaction; an accelerator validatorto determine whether the first authentication tag matches the secondauthentication tag; and a memory mapper to commit the memory-mapped I/Otransaction in response to a determination that the first authenticationtag matches the second authentication tag.

Example 2 includes the subject matter of Example 1, and wherein theaccelerator validator is further to drop the memory-mapped I/Otransaction in response to a determination that the first authenticationtag does not match the second authentication tag.

Example 3 includes the subject matter of any of Examples 1-2, andwherein the memory-mapped I/O transaction comprises a memory-mapped I/Owrite, and wherein: the host cryptographic engine is further to encrypta data item to generate an encrypted data item; to generate the firstauthentication tag comprises to generate the first authentication tag inresponse to encryption of the data item; to dispatch the memory-mappedI/O transaction comprises to dispatch the memory-mapped I/O write withthe encrypted data item; to perform the cryptographic operationcomprises to decrypt the encrypted data item to generate the data item;to generate the second authentication tag comprises to generate thesecond authentication tag based on the encrypted data item; and tocommit the memory-mapped I/O transaction comprises to store the dataitem in a memory of the accelerator device.

Example 4 includes the subject matter of any of Examples 1-3, andwherein the memory mapper is further to set a status register toindicate success in response to storage of the data item.

Example 5 includes the subject matter of any of Examples 1-4, andwherein the trusted execution environment further comprises a hostvalidator to verify that the memory-mapped I/O write succeeded inresponse to the dispatch of the memory-mapped I/O write.

Example 6 includes the subject matter of any of Examples 1-5, andwherein to verify that the memory-mapped I/O write succeeded comprisesto securely read a status register of the accelerator device.

Example 7 includes the subject matter of any of Examples 1-6, andwherein to verify that the memory-mapped I/O write succeeded comprisesto securely read a value at an address of the memory-mapped I/O writefrom the accelerator device.

Example 8 includes the subject matter of any of Examples 1-7, andwherein to verify that the memory-mapped I/O write succeeded comprisesto securely read a second authentication tag register of the acceleratordevice.

Example 9 includes the subject matter of any of Examples 1-8, andwherein the memory-mapped I/O transaction comprises a memory-mapped I/Oread request, and wherein: to generate the first authentication tagcomprises to generate the first authentication tag based on an addressassociated with the memory-mapped I/O read request; to commit thememory-mapped I/O transaction comprises to read a data item at theaddress in a memory of the accelerator device in response to thedetermination that the first authentication tag matches the secondauthentication tag; and to perform the cryptographic operation furthercomprises to encrypt the data item to generate an encrypted data item inresponse to a read of the data item.

Example 10 includes the subject matter of any of Examples 1-9, andwherein: the accelerator cryptographic engine is further to generate athird authentication tag based on the encrypted data item in response toencryption of the data item; the memory mapper is further to dispatch amemory-mapped I/O read response with the encrypted data item to thetrusted execution environment in response to generation of the thirdauthentication tag; and the trusted execution environment furthercomprises a host validator to: generate a fourth authentication tagbased on the encrypted data item in response to dispatch of thememory-mapped I/O read response; read the third authentication tag froma register of the accelerator device; and determine whether the thirdauthentication tag matches the fourth authentication tag.

Example 11 includes the subject matter of any of Examples 1-10, andwherein the host validator is further to indicate an error in responseto a determination that the third authentication tag does not match thefourth authentication tag.

Example 12 includes the subject matter of any of Examples 1-11, andwherein the accelerator validator is further to: drop the memory-mappedI/O read request in response to a determination that the firstauthentication tag does not match the second authentication tag; andgenerate a poisoned authentication tag in response to dropping of thememory-mapped I/O read request.

Example 13 includes the subject matter of any of Examples 1-12, andwherein the accelerator validator is further to dispatch a memory-mappedI/O read response with a poisoned data item to the trusted executionenvironment in response to the dropping of the memory-mapped I/O readrequest.

Example 14 includes the subject matter of any of Examples 1-13, andwherein the accelerator device comprises a field-programmable gate array(FPGA).

Example 15 includes the subject matter of any of Examples 1-14, andwherein the trusted execution environment comprises a secure enclaveestablished with secure enclave support of a processor of the computingdevice.

Example 16 includes a computing device for secure data transfer, thecomputing device comprising a trusted execution environment and anaccelerator device, wherein the accelerator device comprises: anauthentication tag controller to initialize an authentication tag inresponse to an initialization command from the trusted executionenvironment; a direct memory access engine to transfer data between ahost memory buffer and an accelerator device buffer in response to adescriptor from the trusted execution environment, wherein thedescriptor is indicative of the host memory buffer, the acceleratordevice buffer, and a transfer direction; and an acceleratorcryptographic engine to (i) perform a cryptographic operation with thedata in response to a transfer of the data and (ii) update theauthentication tag in response to the transfer of the data; wherein theauthentication tag controller is further to finalize the authenticationtag in response to a finalization command from the trusted executionenvironment.

Example 17 includes the subject matter of Example 16, and wherein: thetransfer direction comprises host device to accelerator device; toperform the cryptographic operation comprises to decrypt encrypted datato generate plaintext data; and to transfer the data between the hostmemory buffer and the accelerator device buffer comprises to (i) copythe encrypted data from the host memory buffer and (ii) forward theplaintext data to the accelerator device buffer in response todecryption of the encrypted data.

Example 18 includes the subject matter of any of Examples 16 and 17, andwherein: the transfer direction comprises accelerator device to hostdevice; to perform the cryptographic operation comprises to encryptplaintext data to generate encrypted data; and to transfer the databetween the host memory buffer and the accelerator device buffercomprises to (i) copy the plaintext data from the accelerator devicebuffer and (ii) forward the encrypted data to the host memory buffer inresponse to encryption of the plaintext data.

Example 19 includes the subject matter of any of Examples 16-18, andwherein the trusted execution environment comprises a direct memoryaccess manager to: (i) securely write the initialization command to theaccelerator device to initialize the secure DMA transfer, (ii) securelyconfigure the descriptor, and (iii) securely write the finalizationcommand to the accelerator device to finalize the authentication tag.

Example 20 includes the subject matter of any of Examples 16-19, andwherein each of to securely write the initialization command, tosecurely configure the descriptor, and to securely write thefinalization command comprises to dispatch a memory-mapped I/O write.

Example 21 includes the subject matter of any of Examples 16-20, andwherein the trusted execution environment further comprises a hostvalidator to: determine an expected authentication tag based on thesecure DMA transfer; read the authentication tag from the acceleratordevice in response to a secure write of the finalization command; anddetermine whether the authentication tag matches the expectedauthentication tag.

Example 22 includes the subject matter of any of Examples 16-21, andwherein the host validator is further to: indicate success for thesecure DMA transfer in response to a determination that theauthentication tag matches the expected authentication tag; and indicatefailure for the secure DMA transfer in response to a determination thatthe authentication tag does not match the expected authentication tag.

Example 23 includes the subject matter of any of Examples 16-22, andwherein: the direct memory access manager is further to determinewhether to transfer additional data in response to secure configurationof the descriptor; and to securely write the finalization commandcomprises to securely write the finalization command in response to adetermination not to transfer additional data.

Example 24 includes the subject matter of any of Examples 16-23, andwherein the accelerator device comprises a field-programmable gate array(FPGA).

Example 25 includes the subject matter of any of Examples 16-24, andwherein the trusted execution environment comprises a secure enclaveestablished with secure enclave support of a processor of the computingdevice.

Example 26 includes a method for secure data transfer, the methodcomprising: generating, by a trusted execution environment of acomputing device, a first authentication tag based on a memory-mappedI/O transaction; writing, by the trusted execution environment, thefirst authentication tag to an authentication tag register of anaccelerator device of the computing device; dispatching, by the trustedexecution environment, the memory-mapped I/O transaction to theaccelerator device in response to writing the first authentication tag;performing, by the accelerator device, a cryptographic operationassociated with the memory-mapped I/O transaction in response todispatching the memory-mapped I/O transaction; generating, by theaccelerator device, a second authentication tag based on thememory-mapped I/O transaction in response to dispatching thememory-mapped I/O transaction; determining, by the accelerator device,whether the first authentication tag matches the second authenticationtag; and committing, by the accelerator device, the memory-mapped I/Otransaction in response to determining that the first authentication tagmatches the second authentication tag.

Example 27 includes the subject matter of Example 26, and furthercomprising dropping, by the accelerator device, the memory-mapped I/Otransaction in response to determining that the first authentication tagdoes not match the second authentication tag.

Example 28 includes the subject matter of any of Examples 26 and 27, andwherein the memory-mapped I/O transaction comprises a memory-mapped I/Owrite, and wherein: the method further comprises encrypting, by thetrusted execution environment, a data item to generate an encrypted dataitem; generating the first authentication tag comprises generating thefirst authentication tag in response to encrypting the data item;dispatching the memory-mapped I/O transaction comprises dispatching thememory-mapped I/O write with the encrypted data item; performing thecryptographic operation comprises decrypting the encrypted data item togenerate the data item; generating the second authentication tagcomprises generating the second authentication tag based on theencrypted data item; and committing the memory-mapped I/O transactioncomprises storing the data item in a memory of the accelerator device.

Example 29 includes the subject matter of any of Examples 26-28, andfurther comprising setting, by the accelerator device, a status registerto indicate success in response to storing the data item.

Example 30 includes the subject matter of any of Examples 26-29, andfurther comprising verifying, by the trusted execution environment, thatthe memory-mapped I/O write succeeded in response to dispatching thememory-mapped I/O write.

Example 31 includes the subject matter of any of Examples 26-30, andwherein verifying that the memory-mapped I/O write succeeded comprisessecurely reading a status register of the accelerator device.

Example 32 includes the subject matter of any of Examples 26-31, andwherein verifying that the memory-mapped I/O write succeeded comprisessecurely reading a value at an address of the memory-mapped I/O writefrom the accelerator device.

Example 33 includes the subject matter of any of Examples 26-32, andwherein verifying that the memory-mapped I/O write succeeded comprisessecurely reading a second authentication tag register of the acceleratordevice.

Example 34 includes the subject matter of any of Examples 26-33, andwherein the memory-mapped I/O transaction comprises a memory-mapped I/Oread request, and wherein: generating the first authentication tagcomprises generating the first authentication tag based on an addressassociated with the memory-mapped I/O read request; committing thememory-mapped I/O transaction comprises reading a data item at theaddress in a memory of the accelerator device in response to determiningthat the first authentication tag matches the second authentication tag;and performing the cryptographic operation further comprises encryptingthe data item to generate an encrypted data item in response to readingthe data item.

Example 35 includes the subject matter of any of Examples 26-34, andfurther comprising: generating, by the accelerator device, a thirdauthentication tag based on the encrypted data item in response toencrypting the data item; dispatching, by the accelerator device, amemory-mapped I/O read response with the encrypted data item to thetrusted execution environment in response to generating the thirdauthentication tag; generating, by the trusted execution environment, afourth authentication tag based on the encrypted data item in responseto dispatching the memory-mapped I/O read response; reading, by thetrusted execution environment, the third authentication tag from aregister of the accelerator device; and determining, by the trustedexecution environment, whether the third authentication tag matches thefourth authentication tag.

Example 36 includes the subject matter of any of Examples 26-35, andfurther comprising indicating, by the trusted execution environment, anerror in response to determining that the third authentication tag doesnot match the fourth authentication tag.

Example 37 includes the subject matter of any of Examples 26-36, andfurther comprising: dropping, by the accelerator device, thememory-mapped I/O read request in response to determining that the firstauthentication tag does not match the second authentication tag; andgenerating, by the accelerator device, a poisoned authentication tag inresponse to dropping the memory-mapped I/O read request.

Example 38 includes the subject matter of any of Examples 26-37, andfurther comprising dispatching, by the accelerator device, amemory-mapped I/O read response with a poisoned data item to the trustedexecution environment in response to dropping the memory-mapped I/O readrequest.

Example 39 includes the subject matter of any of Examples 26-39, andwherein the accelerator device comprises a field-programmable gate array(FPGA).

Example 40 includes the subject matter of any of Examples 26-40, andwherein the trusted execution environment comprises a secure enclaveestablished with secure enclave support of a processor of the computingdevice.

Example 41 includes a method for secure data transfer, the methodcomprising: initializing, by an accelerator device of a computingdevice, an authentication tag in response to an initialization commandfrom a trusted execution environment of the computing device;transferring, by the accelerator device, data between a host memorybuffer and an accelerator device buffer in response to a descriptor fromthe trusted execution environment, wherein the descriptor is indicativeof the host memory buffer, the accelerator device buffer, and a transferdirection; performing, by the accelerator device, a cryptographicoperation with the data in response to transferring the data; updating,by the accelerator device, the authentication tag in response totransferring the data; and finalizing, by the accelerator device, theauthentication tag in response to a finalization command from thetrusted execution environment.

Example 42 includes the subject matter of Example 41, and wherein: thetransfer direction comprises host device to accelerator device;performing the cryptographic operation comprises decrypting encrypteddata to generate plaintext data; and transferring the data between thehost memory buffer and the accelerator device buffer comprises (i)copying the encrypted data from the host memory buffer and (ii)forwarding the plaintext data to the accelerator device buffer inresponse to decrypting the encrypted data.

Example 43 includes the subject matter of any of Examples 41 and 42, andwherein: the transfer direction comprises accelerator device to hostdevice; performing the cryptographic operation comprises encryptingplaintext data to generate encrypted data; and transferring the databetween the host memory buffer and the accelerator device buffercomprises (i) copying the plaintext data from the accelerator devicebuffer and (ii) forwarding the encrypted data to the host memory bufferin response to encrypting the plaintext data.

Example 44 includes the subject matter of any of Examples 41-43, andfurther comprising: securely writing, by the trusted executionenvironment, the initialization command to the accelerator device toinitialize the secure DMA transfer; securely configuring, by the trustedexecution environment, the descriptor; and securely writing, by thetrusted execution environment, the finalization command to theaccelerator device to finalize the authentication tag.

Example 45 includes the subject matter of any of Examples 41-44, andwherein each of securely writing the initialization command, securelyconfiguring the descriptor, and securely writing the finalizationcommand comprises dispatching a memory-mapped I/O write.

Example 46 includes the subject matter of any of Examples 41-45, andfurther comprising: determining, by the trusted execution environment,an expected authentication tag based on the secure DMA transfer;reading, by the trusted execution environment, the authentication tagfrom the accelerator device in response to securely writing thefinalization command; and determining, by the trusted executionenvironment, whether the authentication tag matches the expectedauthentication tag.

Example 47 includes the subject matter of any of Examples 41-46, andfurther comprising: indicating, by the trusted execution environment,success for the secure DMA transfer in response to determining that theauthentication tag matches the expected authentication tag; andindicating, by the trusted execution environment, failure for the secureDMA transfer in response to determining that the authentication tag doesnot match the expected authentication tag.

Example 48 includes the subject matter of any of Examples 41-47, andfurther comprising: determining, by the trusted execution environment,whether to transfer additional data in response to securely configuringthe descriptor; wherein securely writing the finalization commandcomprises securely writing the finalization command in response todetermining not to transfer additional data.

Example 49 includes the subject matter of any of Examples 41-48, andwherein the accelerator device comprises a field-programmable gate array(FPGA).

Example 50 includes the subject matter of any of Examples 41-49, andwherein the trusted execution environment comprises a secure enclaveestablished with secure enclave support of a processor of the computingdevice.

Example 51 includes a computing device comprising: a processor; and amemory having stored therein a plurality of instructions that whenexecuted by the processor cause the computing device to perform themethod of any of Examples 26-50.

Example 52 includes one or more non-transitory, computer readablestorage media comprising a plurality of instructions stored thereon thatin response to being executed result in a computing device performingthe method of any of Examples 26-50.

Example 53 includes a computing device comprising means for performingthe method of any of Examples 26-50.

1. A computing device for secure data transfer, the computing devicecomprising: a processor having a trusted execution environment, theprocessor coupled to an accelerator device, the accelerator devicecomprising: an authentication tag controller to initialize anauthentication tag in response to an initialization command from thetrusted execution environment; a direct memory access engine to transferdata between a host memory buffer and an accelerator device buffer inresponse to a descriptor from the trusted execution environment, whereinthe descriptor is indicative of the host memory buffer, the acceleratordevice buffer, and a transfer direction; and an acceleratorcryptographic engine to (i) perform a cryptographic operation with thedata in response to a transfer of the data and (ii) update theauthentication tag in response to the transfer of the data; wherein theauthentication tag controller is further to finalize the authenticationtag in response to a finalization command from the trusted executionenvironment.
 2. The computing device of claim 1, wherein: the transferdirection comprises host device to accelerator device; to perform thecryptographic operation comprises to decrypt encrypted data to generateplaintext data; and to transfer the data between the host memory bufferand the accelerator device buffer comprises to (i) copy the encrypteddata from the host memory buffer and (ii) forward the plaintext data tothe accelerator device buffer in response to decryption of the encrypteddata.
 3. The computing device of claim 1, wherein: the transferdirection comprises accelerator device to host device; to perform thecryptographic operation comprises encrypted plaintext data to generateencrypted data; and to transfer the data between the host memory bufferand the accelerator device buffer comprises to (i) copy the plaintextdata from the accelerator device buffer and (ii) forward the encrypteddata to the host memory buffer in response to encryption of theplaintext data.
 4. The computing device of claim 1, wherein the trustedexecution environment comprises a direct memory access manager to: (i)securely write the initialization command to the accelerator device toinitialize the secure DMA transfer, (ii) securely configure thedescriptor, and (iii) securely write the finalization command to theaccelerator device to finalize the authentication tag.
 5. The computingdevice of claim 4, wherein each of to securely write the initializationcommand, to securely configure the descriptor, and to securely write thefinalization command comprises to dispatch a memory-mapped I/O write. 6.The computing device of claim 4, wherein the trusted executionenvironment further comprises a host validator to: determine an expectedauthentication tag based on the secure DMA transfer; read theauthentication tag from the accelerator device in response to a securewrite of the finalization command; and determine whether theauthentication tag matches the expected authentication tag.
 7. Thecomputing device of claim 4, wherein: the direct memory access manageris further to determine whether to transfer additional data in responseto secure configuration of the descriptor; and to securely write thefinalization command comprises to securely write the finalizationcommand in response to a determination not to transfer additional data.8. One or more computer-readable storage media comprising a plurality ofinstructions stored thereon that, in response to being executed, cause acomputing device to perform operations comprising: initializing, by anaccelerator device of the computing device, an authentication tag inresponse to an initialization command from a trusted executionenvironment of the computing device; transferring, by the acceleratordevice, data between a host memory buffer and an accelerator devicebuffer in response to a descriptor from the trusted executionenvironment, wherein the descriptor is indicative of the host memorybuffer, the accelerator device buffer, and a transfer direction;performing, by the accelerator device, a cryptographic operation withthe data in response to transferring the data; updating, by theaccelerator device, the authentication tag in response to transferringthe data; and finalizing, by the accelerator device, the authenticationtag in response to a finalization command from the trusted executionenvironment.
 9. The one or more computer-readable storage media of claim8, wherein: performing the cryptographic operation comprises decryptingencrypted data to generate plaintext data; and transferring the databetween the host memory buffer and the accelerator device buffercomprises (i) copying the encrypted data from the host memory buffer and(ii) forwarding the plaintext data to the accelerator device buffer inresponse to decrypting the encrypted data.
 10. The one or morecomputer-readable storage media of claim 8, wherein: performing thecryptographic operation comprises encrypting plaintext data to generateencrypted data; and transferring the data between the host memory bufferand the accelerator device buffer comprises (i) copying the plaintextdata from the accelerator device buffer and (ii) forwarding theencrypted data to the host memory buffer in response to encrypting theplaintext data.
 11. The one or more computer-readable storage media ofclaim 8, wherein the operations further comprise: securely writing, bythe trusted execution environment, the initialization command to theaccelerator device to initialize the secure DMA transfer; securelyconfiguring, by the trusted execution environment, the descriptor; andsecurely writing, by the trusted execution environment, the finalizationcommand to the accelerator device to finalize the authentication tag.12. The one or more computer-readable storage media of claim 11, whereinthe operations further comprise: determining, by the trusted executionenvironment, an expected authentication tag based on the secure DMAtransfer; reading, by the trusted execution environment, theauthentication tag from the accelerator device in response to securelywriting the finalization command; and determine, by the trustedexecution environment, whether the authentication tag matches theexpected authentication tag.
 13. A method comprising: initializing, byan accelerator device of the computing device, an authentication tag inresponse to an initialization command from a trusted executionenvironment of the computing device; transferring, by the acceleratordevice, data between a host memory buffer and an accelerator devicebuffer in response to a descriptor from the trusted executionenvironment, wherein the descriptor is indicative of the host memorybuffer, the accelerator device buffer, and a transfer direction;performing, by the accelerator device, a cryptographic operation withthe data in response to transferring the data; updating, by theaccelerator device, the authentication tag in response to transferringthe data; and finalizing, by the accelerator device, the authenticationtag in response to a finalization command from the trusted executionenvironment.
 14. The method of claim 13, further comprising: performingthe cryptographic operation comprises decrypting encrypted data togenerate plaintext data; and transferring the data between the hostmemory buffer and the accelerator device buffer comprises (i) copyingthe encrypted data from the host memory buffer and (ii) forwarding theplaintext data to the accelerator device buffer in response todecrypting the encrypted data.
 15. The method of claim 13, furthercomprising: performing the cryptographic operation comprises encryptingplaintext data to generate encrypted data; and transferring the databetween the host memory buffer and the accelerator device buffercomprises (i) copying the plaintext data from the accelerator devicebuffer and (ii) forwarding the encrypted data to the host memory bufferin response to encrypting the plaintext data.
 16. The method of claim13, further comprising: securely writing, by the trusted executionenvironment, the initialization command to the accelerator device toinitialize the secure DMA transfer; securely configuring, by the trustedexecution environment, the descriptor; and securely writing, by thetrusted execution environment, the finalization command to theaccelerator device to finalize the authentication tag.
 17. The method ofclaim 16, further comprising: determining, by the trusted executionenvironment, an expected authentication tag based on the secure DMAtransfer; reading, by the trusted execution environment, theauthentication tag from the accelerator device in response to securelywriting the finalization command; and determine, by the trustedexecution environment, whether the authentication tag matches theexpected authentication tag.